Abstract Sorption-induced strain of coal is vital to the prediction of coal bed methane production and stimulation. Previous studies have addressed the relationship between strain and equilibrium pressure and the relationship between strain change and permeability evolution. However, the strain variations with respect to time and the comparison between the asynchronous difference of dynamic characteristics of adsorption swelling and mechanical compression were rarely explored. In this study, we investigated the anisotropy characteristics of strain change over time as well as the influence of the gas species, gas pressure, and pore structure on the dynamic strain variations by using the low temperature liquid nitrogen adsorption method and a self-designed coal strain measurement apparatus. Our results show that gas diffusion rate has a strong influence on sorption-induced strain of coal. Both mechanical compression and sorption-induced strain exhibited an asynchronous effect with respect to saturating time. We then propose a time-depended volumetric deformation model for coal to analyze the mechanism of the asynchronous effect during sorption. This study sheds light on the dynamic process of coal bed methane production and reveals restrictions of current permeability models.

中文翻译：

---

煤吸附膨胀与机械压缩动态特性的异步差异：建模与实验

摘要 煤的吸附诱导应变对于预测煤层气生产和增产至关重要。以前的研究已经解决了应变与平衡压力之间的关系以及应变变化与渗透率演变之间的关系。然而，很少探索应变随时间的变化以及吸附膨胀和机械压缩动态特性的异步差异之间的比较。在这项研究中，我们利用低温液氮吸附方法和自行设计的煤研究了应变随时间变化的各向异性特征以及气体种类、气体压力和孔隙结构对动态应变变化的影响。应变测量仪。我们的研究结果表明，气体扩散速率对煤的吸附诱导应变有很大的影响。机械压缩和吸附诱导应变都表现出关于饱和时间的异步效应。然后，我们提出了煤的时间相关体积变形模型，以分析吸附过程中异步效应的机制。这项研究揭示了煤层气生产的动态过程，并揭示了当前渗透率模型的局限性。